Good guardian, bad parent: tradeoffs between territory defense and parental care in Darwin’s finches

Although defending a territory may benefit individuals by allowing them to retain important resources, the time and energy costs associated with territory defense may lead territory owners to neglect other reproductively important behaviors. In this study, we assessed the potential trade-off between territory defense and parental care in four Darwin’s finch species on Floreana Island, Galápagos. First, using song playback, we simulated territory intrusions to measure male aggressiveness across multiple stages of the breeding cycle (unpaired, paired, incubating, and chick feeding). We conducted 168 playback trials at 98 nests (37 small ground finch, 28 medium tree finch, 27 small tree finch, 6 cactus finch). To quantify parental care at each nest, we conducted one-hour observations to record the frequency of male food deliveries and the duration of female incubation and brooding. We conducted 113 parental care observations at 59 nests (24 small ground finch, 18 small tree finch, 15 mediu..., Study sites and species
We conducted our study from January to March 2024 on Floreana Island in the Galápagos archipelago, at two highland (humid zone) sites and one lowland (dry zone) site. The two highland sites, located at Asilo de la Paz (1°18’46” S 90°27’16 ”W) and the base of Cerro Pajas (1°17’46” S 90°27’06” W), consisted largely of remnant Scalesia pedunculata forest. The one lowland (dry zone) site comprised dry scrubland dominated by palo santo trees (Bursera graveolens) in and around the township of Puerto Velasco Ibarra (1°16’28” S 90°29’13” W). Our study included four of the five Darwin’s finch species considered extant on the island: the small ground finch (Geospiza fuliginosa), common cactus finch (Geospiza scandens), small tree finch (Camarhynchus parvulus), and medium tree finch (Camarhynchus pauper). Small ground finches and small tree finches were present at all three sites, medium tree finches only breed at the two highland sites, and cactus finches only at the lowla..., # Good guardian, bad parent: tradeoffs between territory defense and parental care in Darwin’s finches

Andrew C. Katsis^1,2*^, Lauren K. Common^1,2^, Çağlar Akçay^3^, Sonia Kleindorfer^1,2,4^

1. Konrad Lorenz Research Center for Behavior and Cognition, University of Vienna, Grünau im Almtal, Austria
2. Department of Behavioral and Cognitive Biology, University of Vienna, Vienna, Austria
3. School of Life Sciences, Anglia Ruskin University, Cambridge, United Kingdom
4. College of Science and Engineering, Flinders University, Adelaide, South Australia, Australia

*Corresponding author: [[e-mail]](mailto:[e-mail])

#### **Description of the data and file structure**

*Full details for this dataset are given in Katsis et al. (2025,*Behavioral Ecology*).

#### **Files and variables**

***File: TerritoryDefense.csv***

**Description:** This file contains the behavioral responses of male Darwin's finches to simulated territory intrusions. Playback trials were...,